!11241 optimize the dynamic memory alloc

From: @limingqi107
Reviewed-by: @cristoval,@kisnwang
Signed-off-by: @kisnwang

mindspore/ccsrc/backend/optimizer/mem_reuse/mem_dynamic_allocator.h

@@ -33,8 +33,8 @@ enum DynamicMemBufStatus : int { kMemBufIdle, kMemBufUsed };
 // Alloc memory aligned according to 512 bytes.
 static const size_t DYNAMIC_MEM_ALIGN_SIZE = 512;
 
-// The minimum unit size (500M) of memory block used for dynamic extend.
-static const size_t DYNAMIC_MEM_ALLOC_UNIT_SIZE = 500 << 20;
+// The minimum unit size (1G) of memory block used for dynamic extend.
+static const size_t DYNAMIC_MEM_ALLOC_UNIT_SIZE = 1024 << 20;
 
 // The Comparator of device address from small to large.
 struct DeviceAddrCmp {

mindspore/ccsrc/runtime/device/ascend/ascend_memory_pool.cc

@@ -76,7 +76,7 @@ size_t AscendMemoryPool::AlignMemorySize(size_t size) const {
   return size;
 }
 
-size_t AscendMemoryPool::mem_alloc_unit_size() const { return DYNAMIC_MEM_ALLOC_UNIT_SIZE / 2; }
+size_t AscendMemoryPool::mem_alloc_unit_size() const { return DYNAMIC_MEM_ALLOC_UNIT_SIZE / 4; }
 
 void AscendMemoryPool::set_device_mem_pool_base(uint8_t *device_mem_pool_base) {
   MS_EXCEPTION_IF_NULL(device_mem_pool_base);